Refactors Frame
Makefile fix
Query refactorings
Uses JsonCpp instead of rapidjson for Json namespace; refactors Json;
Removes rapidjson from C++ package requirements
Adds `std::string` related functions to `string.hpp` to allow compiler firewalling (boost string related header not needed for compiling against Stencila library)
More string related changes
Add string tests and alter `string()` function to produce human friendly strings.